1. Field of the Invention
The present invention relates to fibers, methods of making fibers and to products made thereof. In another aspect, the present invention relates to polypropylene fibers, to methods of making such polypropylene fibers, and to products made from such polypropylene fibers. In even another aspect, the present invention relates to fibers comprising isotactic polypropylene and syndiotactic polypropylene, to methods of making such fibers comprising isotactic polypropylene and syndiotactic polypropylene, and to products made from such fibers comprising isotactic polypropylene and syndiotactic polypropylene. In still another aspect, the present invention relates to bicomponent fibers of isotactic polypropylene and syndiotactic polyproplene, to methods of making such bicomponent fibers of isotactic polypropylene and syndiotactic polyproplene, and to products made from such bicomponent fibers of isotactic polypropylene and syndiotactic polyproplene.
2. Description of the Related Art
Polypropylene with its high melting point, high strength, strain resistance and low cost has found employment in a wide variety of applications. Polypropylene fibers have found commercial use in synthetic carpets, geotextiles, textile fabrics, and the like. However, while polypropylene fibers have found wide application as carpet yarns, polypropylene fibers lack the elasticity and resiliency of other carpet fiber polymers, for example nylon. When loads such as furniture legs rest on polypropylene carpets for an extended period and removed, they leave their impression on the carpet in the form of packed carpet fibers. Poor resiliency prevents the packed fibers from bouncing back to their original configuration.
Bicomponent fibers comprise a first polymer component and a second component, with each component fused to the other along the fiber axis. The first and second components may by related as core and sheath, side by side, tipped, mocro denier and mixed fibers, and are generally produced utilizing a specially equipped fiber spinning machine. Examples of bicomponent fibers include nylon and polyurethane, and polypropylene and ethylene copolymers.
Bicomponent fibers of isotactic polypropylene and syndiotactic polypropylene are not known in the art.
Polypropylene has long been known to exist in several forms. Isotactic propylene (iPP) may generally be described as having methyl groups attached to the tertiary carbon atoms of successive monomeric units on the same side of a hypothetical plane through the polymer chain. Syndiotactic polypropylene (sPP) may generally be described as having methyl groups attached on alternating sides of the polymer chain.
Various combinations of syndiotactic and isotactic polypropylene have been proposed.
U.S. Pat. No. 4,939,202, issued Jul. 3, 1990 to Maletsky et al. discloses a barrier guard moisture-proof adhesive coating comprising isotactic and syndiotactic polypropylene. The amorphous polypropylene is said to be formed in minor amounts during the production of crystalline propylene using known sterospecific catalysts.
U.S. Pat. No. 5,124,404, issued Jun. 23, 1992 to Atwell et al. discloses the grafting of brominated monomeric units onto syndiotactic or isotactic polypropylene to form flame retardant polymer.
U.S. Pat. No. 5,269,807, issued Dec. 14, 1993 to Liu discloses a suture fabricated from a blend of comprising syndiotactic and isotactic polypropylene.
E.P. Patent Application No. 0 622 410 A1, published Nov. 2, 1994, discloses melt blending of syndiotactic polypropylene and isotactic polypropylene to form useful medical articles.
E.P. Patent Application No. 0 650 816 A1, published May 3, 1995, discloses injection molding blends of syndiotactic polypropylene and isotactic polypropylene. The blend is made by melt blending syndiotactic polypropylene and isotactic polypropylene.
E.P. Patent Application No. 650,818, published May 3, 1995, discloses a method of forming a film by tubular film extrusion of a polypropylene resin composition comprising syndiotactic polypropylene and isotactic polypropylene. The blend is made by melt blending syndiotactic polypropylene and isotactic polypropylene.
U.S. Pat. No. 5,444,125, issued Aug. 22, 1995 to Tomita et al. discloses laminated olefin polymers obtained by introducing an amino group, into the terminal unsaturated isotactic or syndiotactic alpha-olefin polymer having an olefinic unsaturated bond at its terminus.
U.S. Pat. No. 5,455,305, issued Oct. 3, 1995 to Galambos discloses yarn made from blends of syndiotactic polypropylene and isotactic polypropylene.
U.S. Pat. No. 5,459,117, issued Oct. 17, 1995 to Ewen discloses doubly-conformationally locked, stereorigid catalysts for the preparation of tactiospecific polymers. Specifically, a double-conformationally locked metallocene, i.e., the chain-end is locked conformationally by two sterically different substituents at the distal ring carbon atoms of the cyclopentadienyl radical. The catalysts can be designed to impart any degree of tacticity to the resulting polymers by varying the substituents at the distal ring carbon atoms.
There is still a need in the art for bicomponent fibers of isotactic polypropylene and syndiotactic polypropylene.
These and other needs in the art will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.